U.S. patent application number 13/105138 was filed with the patent office on 2012-11-15 for dual fuel injector and engine using same.
This patent application is currently assigned to Caterpillar Inc.. Invention is credited to Xiangdong Ding, Hoisan Kim, Mark F. Sommars.
Application Number | 20120285417 13/105138 |
Document ID | / |
Family ID | 46086083 |
Filed Date | 2012-11-15 |
United States Patent
Application |
20120285417 |
Kind Code |
A1 |
Kim; Hoisan ; et
al. |
November 15, 2012 |
Dual Fuel Injector And Engine Using Same
Abstract
A dual fuel injector may be used to injector both gas and liquid
fuel into a cylinder of a compression ignition engine. An injector
body defines a first set of nozzle outlets, a second set of nozzle
outlets, a first fuel inlet and a second fuel inlet. A dual
solenoid actuator includes a first armature, a first coil, a second
armature and a second coil that share a common centerline. The dual
solenoid actuator has a non-injection configuration at which the
first armature is at an un-energized position and the second
armature is at an un-energized position. The dual solenoid actuator
has a first fuel injection configuration at which the first fuel
inlet is fluidly connected to the first set of nozzle outlets, the
first armature is at an energized position and the second armature
is at the un-energized position. The dual solenoid actuator has a
second fuel injection configuration at which the second fuel inlet
is fluidly connected to the second set of nozzle outlets, the first
armature is at the un-energized position and the second armature is
at an energized position. The dual solenoid actuator may also
include a combined fuel injection configuration.
Inventors: |
Kim; Hoisan; (Dunlap,
IL) ; Ding; Xiangdong; (Peoria, IL) ; Sommars;
Mark F.; (Hopewell, IL) |
Assignee: |
Caterpillar Inc.
Peoria
IL
|
Family ID: |
46086083 |
Appl. No.: |
13/105138 |
Filed: |
May 11, 2011 |
Current U.S.
Class: |
123/299 ;
123/27GE; 123/304; 123/525; 123/526 |
Current CPC
Class: |
F02M 2200/46 20130101;
F02D 19/10 20130101; F02M 51/0625 20130101; Y02T 10/30 20130101;
F02M 47/027 20130101; F02M 2200/44 20130101; F02M 45/086 20130101;
F02D 19/0615 20130101; F02M 43/04 20130101; F02M 63/029 20130101;
F02D 19/0694 20130101; F02D 19/0684 20130101 |
Class at
Publication: |
123/299 ;
123/27.GE; 123/525; 123/526; 123/304 |
International
Class: |
F02D 19/10 20060101
F02D019/10; F02B 7/02 20060101 F02B007/02; F02M 43/04 20060101
F02M043/04 |
Claims
1. A fuel injector comprising: an injector body defining a first
set of nozzle outlets, a second set of nozzle outlets, a first fuel
inlet and a second fuel inlet; a dual solenoid actuator that
includes a first armature, a first coil, a second armature and a
second coil that share a common centerline; the dual solenoid
actuator having a non-injection configuration at which the first
armature is at an un-energized position and the second armature is
at an un-energized position; the dual solenoid actuator having a
first fuel injection configuration at which the first fuel inlet is
fluidly connected to the first set of nozzle outlets, the first
armature is at an energized position and the second armature is at
the un-energized position; and the dual solenoid actuator having a
second fuel injection configuration at which the second fuel inlet
is fluidly connected to the second set of nozzle outlets, the first
armature is at the un-energized position and the second armature is
at an energized position.
2. The fuel injector of claim 1 including a first needle valve
member movable in the injector body between an open position and a
closed position along a first centerline; and a second needle valve
member movable in the injector body between an open position and a
closed position along a second centerline that is parallel to, but
offset from, the first centerline.
3. The fuel injector of claim 2 wherein the first needle valve
member has a closing hydraulic surface exposed to fluid pressure in
a first control chamber; the second needle valve member has a
closing hydraulic surface exposed to fluid pressure in a second
control chamber; and each of the first control chamber and the
second control chamber are fluidly connected to the first fuel
inlet.
4. The fuel injector of claim 2 including a first control valve
member operably coupled to move into and out of contact with a
first valve seat responsive to movement of the first armature
between the un-energized position and the energized position,
respectively; and a second control valve member operably coupled to
move into and out of contact with a second valve seat responsive to
movement of the second armature between the un-energized position
and the energized position, respectively.
5. The fuel injector of claim 4 wherein the first control valve
member and the second control valve member are biased toward
contact with the first valve seat and the second valve seat,
respectively, by a shared spring.
6. The fuel injector of claim 5 wherein the first control valve
member and the second control valve member move along the common
centerline.
7. The fuel injector of claim 1 wherein the dual solenoid actuator
has a combined fuel injection configuration at which the first set
of nozzle outlets is fluidly connected to the first fuel inlet, the
second fuel inlet is fluidly connected to the second set of nozzle
outlets, the first armature is at the energized position and the
second armature is at the energized position.
8. An engine comprising: an engine housing defining a plurality of
cylinders a dual fuel system including a plurality of fuel
injectors, each including an injector body defining a first set of
nozzle outlets and a second set of nozzle outlets positioned for
direct injection into one of the plurality of cylinders; the dual
fuel system including a first fuel common rail fluidly connected to
a first fuel inlet of each of the plurality of fuel injectors, and
a second fuel common rail fluidly connected to a second fuel inlet
of each of the plurality of fuel injectors; and each of the
plurality of fuel injectors including a dual solenoid actuator that
includes a first armature, a first coil, a second armature and a
second coil that share a common centerline.
9. The engine of claim 8 wherein the dual fuel system including a
plurality of outer tubes, each extending into the engine housing
between a quill and one of the fuel injectors; and the dual fuel
system including a plurality of inner tubes, each extending into
the engine housing through one of the outer tubes and being
compressed between a conical seat on the quill and a conical seat
on the one of the fuel injectors.
10. The engine of claim 8 wherein the first common rail is fluidly
connected to a source of liquified natural gas and the second
common rail is fluidly connected to a source of liquid compression
ignition fuel.
11. The engine of claim 8 wherein each of the plurality of fuel
injectors includes a first needle valve member movable in the
injector body between an open position and a closed position along
a first centerline, and a second needle valve member movable in the
injector body between an open position and a closed position along
a second centerline that is parallel to, but offset from, the first
centerline.
12. The engine of claim 8 wherein each of the plurality of fuel
injectors includes a first needle valve member with a closing
hydraulic surface exposed to fluid pressure in a first control
chamber, and second needle valve member with a closing hydraulic
surface exposed to fluid pressure in a second control chamber, and
each of the first control chamber and the second control chamber
are fluidly connected to the first fuel inlet.
13. The engine of claim 8 wherein the dual solenoid actuator has a
non-injection configuration at which the first armature is at an
un-energized position and the second armature is at an un-energized
position; the dual solenoid actuator has a first fuel injection
configuration at which the first fuel inlet is fluidly connected to
the first set of nozzle outlets, the first armature is at an
energized position and the second armature is at the un-energized
position; the dual solenoid actuator has a second fuel injection
configuration at which the second fuel inlet is fluidly connected
to the second set of nozzle outlets, the first armature is at the
un-energized position and the second armature is at an energized
position; and the dual solenoid actuator has a combined fuel
injection configuration at which the first set of nozzle outlets is
fluidly connected to the first fuel inlet, the second fuel inlet is
fluidly connected to the second set of nozzle outlets, the first
armature is at the energized position and the second armature is at
an energized position.
14. The engine of claim 8 wherein each of the plurality of fuel
injectors include a first control valve member operably coupled to
move into and out of contact with a first valve seat responsive to
movement of the first armature between the un-energized position
and the energized position, respectively; and each of the plurality
of fuel injectors includes a second control valve member operably
coupled to move into and out of contact with a second valve seat
responsive to movement of the second armature between the
un-energized position and the energized position, respectively.
15. A method of operating an engine comprising the steps of:
injecting a first fuel into an engine cylinder through a first set
of nozzle outlets of one of a plurality of fuel injectors; and
injecting a second fuel into the engine cylinder through a second
set nozzle outlets of the one of the plurality of fuel injectors;
each of the injecting steps includes moving one of a first armature
and a second armature toward an other of the first armature and the
second armature along a common centerline; igniting the first fuel
by compression igniting the second fuel.
16. The method of claim 15 wherein the first fuel is natural gas
and the second fuel is diesel fuel.
17. The method of claim 15 wherein the step of injecting the first
fuel includes moving a first control valve member along the common
centerline; the step of injecting the second fuel includes moving a
second control valve member along the common centerline.
18. The method of claim 15 wherein the injecting steps are
performed simultaneously.
19. The method of claim 18 including a step of biasing a first
control valve member of each of the plurality of fuel injectors
toward a closed position with a shared spring; and biasing a second
control valve member of each of the plurality of fuel injectors
toward a closed position with the shared spring.
20. The method of claim 19 wherein the step of injecting the first
fuel includes moving the first control valve member along the
common centerline; the step of injecting the second fuel includes
moving a second control valve member along the common centerline.
Description
TECHNICAL FIELD
[0001] The present disclosure relates generally to dual fuel
engines, and more particularly to a dual fuel injector with a
coaxial dual solenoid actuator for fueling an engine with gaseous
and liquid fuels.
BACKGROUND
[0002] Gaseous fuel engines are known for their ability to burn
clean relative to their compression ignition engine counterparts.
However, gaseous fuels are well known for the difficulty in
attaining successful ignition. Some gaseous fuel engines utilize a
spark plug, whereas other engines are known for utilizing a small
amount of distillate diesel fuel that is compression ignited to in
turn ignite a larger charge of gaseous fuel. Practical spatial
limitations in and around an engine often make it difficult to find
space for all of the plumbing and hardware associated with
supplying two different fuels to each combustion chamber. U.S. Pat.
No. 7,373,931 teaches a dual fuel engine that utilizes a small
quantity and compression ignited distillate diesel fuel to ignite a
larger charge of gaseous fuel. This reference teaches the use of a
fuel injector with nested needle valve members to facilitate
injection of both the gaseous and liquid fuels from the same
injector into each engine cylinder. However, the structure of the
injector can lead to cross leakage between fuels, leakage of fuel
into the engine cylinder and stacked tolerances that may lead to
substantial performance variations when the fuel injectors are mass
produced. In addition, the injector structure inherently requires
different injection patterns depending upon whether the fuels are
being injected individually or at the same time.
[0003] Apart from the potential problems noted above, there may
also be issues with regard to packaging a dual fuel injector with
two electrical actuators and control valves in the limited space
available in a cylinder head mounting of an engine. The '931 patent
shows side-by-side electronically controlled valves for separately
controlling gaseous fuel and liquid fuel injection events. In some
instances, there may not be enough available space to provide for a
side-by-side mounting as shown in this reference.
[0004] The present disclosure is directed toward one or more of the
problems set forth above.
SUMMARY OF THE DISCLOSURE
[0005] In one aspect, a fuel injector includes an injector body
that defines a first set of nozzle outlets, a second set of nozzle
outlets, a first fuel inlet and a second fuel inlet. A dual
solenoid actuator includes a first armature, a first coil, a second
armature and a second coil that share a common centerline. The dual
solenoid actuator has a non-injection configuration at which the
first armature is at an un-energized position and the second
armature is at an un-energized position. The dual solenoid actuator
has a first fuel injection configuration at which the first fuel
inlet is fluidly connected to the first set of nozzle outlets, the
first armature is at an energized position and the second armature
is at the un-energized position. The dual solenoid actuator has a
second fuel injection configuration at which the second fuel inlet
is fluidly connected to the second set of nozzle outlets, the first
armature is at the un-energized position and the second armature is
at an energized position.
[0006] In another aspect, an engine includes an engine housing that
defines a plurality of cylinders. A dual fuel system includes a
plurality of fuel injectors, each including an injector body
defining a first set of nozzle outlets and a second set of nozzle
outlets positioned for direct injection into one of the plurality
of cylinders. The duel fuel system includes a first fuel common
rail fluidly connected to a first fuel inlet of each of the
plurality of fuel injectors, and a second fuel common rail fluidly
connected to a second fuel inlet of each of the plurality of fuel
injectors. Each of the plurality of fuel injectors includes a dual
solenoid actuator that includes a first armature, a first coil, a
second armature and a second coil that share a common
centerline.
[0007] A method of operating an engine includes a step of injecting
a first fuel into an engine cylinder through a first set of nozzle
outlets of one of a plurality of fuel injectors. A second fuel is
injected into the engine cylinder through a second set of nozzle
outlets of the one of the plurality of fuel injectors. Each of the
injecting steps includes moving one of a first armature and a
second armature toward an other of the first armature and the
second armature along a common centerline. The first fuel is
ignited by compression igniting the second fuel.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a schematic view of an engine and dual fuel common
rail system according to the present disclosure.
[0009] FIG. 2 is a side sectioned view of a portion of the dual
fuel system of FIG. 1;
[0010] FIG. 3 is a sectioned side view of a top portion of one of
the dual fuel injectors from FIG. 1;
[0011] FIG. 4 is a sectioned side view of a bottom portion of a
fuel injector according to one aspect of the present
disclosure;
[0012] FIG. 5 is a sectioned side bottom portion view of a fuel
injector according to another aspect of the present disclosure;
and
[0013] FIG. 6 is a series of graphs showing control valve
positions, gaseous and liquid fuel rail pressures and injection
rates verses time for the dual fuel system of FIG. 1 when operating
in a dual fueling mode and a limp home mode.
DETAILED DESCRIPTION
[0014] Referring to FIG. 1, an engine 5 according to the present
disclosure utilizes a dual fuel common rail system 10. Engine 5
includes an engine housing 6 that defines a plurality of cylinders
7, only one of which is shown. The dual fuel system 10 includes a
plurality of dual fuel injectors 12 (only one shown) that each
include an injector body 70 with a tip component 71 positioned for
direct injection of gaseous fuel and/or liquid fuel into one of the
engine cylinders 7. The dual fuel system 10 includes a plurality of
outer tubes 50 and inner tubes 40 that each extend into engine
housing 6 between a quill 30 and one of the fuel injectors 12. Each
of the inner tubes 50 is compressed between a conical seat on an
associated quill 30 and a conical seat on one of the fuel injectors
12. Thus, each engine cylinder 7 has one associated fuel injector
12, one outer tube 40, one inner tube 50 and one quill 30. The dual
fuel system 10 includes a gaseous fuel common rail 16 that is
fluidly connected to each of the fuel injectors 12 through one of
the quills 30 and an outer passage 49 defined between an inner tube
50 and an outer tube 40. A liquid fuel common rail 14 is fluidly
connected to each of the fuel injectors 12 through one of the
quills 30 and an inner passage 51 defined by the inner tube 50.
[0015] An electronic controller 15 is in control communication with
each of the fuel injectors 12 to selectively control the timing and
quantity of both gaseous and liquid fuel injection events.
Electronic controller 15 is also in control communication with a
gas pressure control device 20 that is operably coupled to control
the pressure in gaseous fuel common rail 16, and also in control
communication with a liquid pressure control device 22 operably
coupled to control the pressure in liquid fuel common rail 14.
Although individual gases, such as methane, propane and the like
are within the scope of the present disclosure, natural gas
containing a mixture of gas species is particularly applicable to
the present disclosure. In addition, the liquid fuel is chosen for
the ability for compression ignition at the compression ratio of
engine 5. For instance, the liquid fuel may be distillate diesel
fuel or some other liquid fuel that is suitable for compression
ignition to in turn ignite a charge of gaseous fuel in one of the
engine cylinders 7.
[0016] In the illustrated embodiment, natural gas is maintained in
a liquid state in a cryogenic liquefied natural gas tank 21. A
variable displacement cryogenic pump is controlled by electronic
controller 15 to pump liquefied natural gas through filters and a
heat exchanger for expansion into a gas that is maintained in an
accumulator. The gas pressure control device 20 according to the
present disclosure may include an electronically controlled valve
that supplies a controlled quantity of gaseous fuel from the supply
side (accumulator) to the gaseous fuel common rail 16. This
described supply strategy for natural gas is particularly suitable
when engine 5 is mounted on a moving machine, such as a mining
truck or the like. On the otherhand, if engine 5 were stationary, a
gas pressure control device may be connected to a source of
available natural gas and then compressed and fed to gaseous fuel
common rail 16 in a manner that is controlled by electronic
controller 15 to maintain a desired pressure in the rail 16.
[0017] The liquid fuel supply to liquid fuel common rail 14 begins
at a tank 23. In the illustrated embodiment, the liquid fuel
pressure control device 22 includes a high pressure common rail
fuel pump of a type well known in the art whose output can be
controlled by electronic controller 15 to maintain some desired
pressure in liquid common rail 14. Another alternative might
include fixed displacement pump and a rail pressure control valve
that returns a quantity of the fuel back to tank 23 in order to
control pressure in liquid fuel common rail 14. Any of these
alternative strategies fall within the contemplated scope of the
present disclosure.
[0018] In the event that engine 5 is utilized in a moving machine,
the present disclosure contemplates liquefied natural gas tank 21
having a larger capacity (maybe 65% greater volume) than the
distillate diesel fuel tank 23 in order to account for the expected
ratios of consumption from both tanks when operating in a standard
dual fueling configuration in which maybe over 90% of the fuel
delivery to engine 5 is in the form of natural gas and less than
10% in the form of distillate diesel fuel, by mass. This difference
in sizing of tanks 21 and 23 also accounts for the densities of the
respective liquids as well as the different heating values of the
two fuels, as well as accounting for the fact that the natural gas
is stored as a liquid but injected as a gas, whereas the distillate
diesel fuel is stored and injected as a liquid into engine 5. When
operating in a dual fueling mode corresponding to standard
operation, electronic controller 15 is configured to maintain the
gaseous fuel common rail at a medium low pressure and the liquid
fuel common rail 14 at a medium high pressure. If engine 5 is
operating in a limp home fueling mode, the electronic controller 15
may be configured to maintain the gaseous fuel common rail 16 at a
low pressure and the liquid common rail 14 at a high pressure. For
the sake of clarity, the identified high pressure is greater than
the medium high pressure, which is greater than the medium low
pressure, which is greater than the low pressure.
[0019] Referring to FIG. 2, the dual fuel common rail system 10
includes a coaxial quill assembly 118 fluidly connecting each fuel
injector 12 with liquid and gas common rails 14, 16, respectively.
Although the concepts of the present disclosure could apply to a
variety of fuels for different types of engines, the illustrated
embodiment is particularly suited for a gaseous fuel engine that
utilizes distillate diesel fuel for compression ignition. In other
words, an engine associated with dual fuel common rail system 10
might primarily burn liquefied natural gas supplied from second
common rail 16, and ignite that charge in the engine combustion
space by compression igniting a smaller charge of distillate diesel
fuel from common rail 14 during a combustion event.
[0020] Coaxial quill assembly 118 includes a quill 30 at least
partially positioned in a block 120. The quill includes a first
fuel passage 32 extending between a first fuel inlet 33, which is
fluidly connected to first common rail 14, and a first fuel outlet
34. Quill 30 also defines a second fuel passage 35 extending
between a second fuel inlet 36, which is fluidly connected to
second common rail 16, and a second fuel outlet 37. Quill 30 is
fluidly connected to rails 14 and 16 using known hardware (e.g.,
fittings) and techniques. Fuel from first common rail 14 is moved
through an engine housing 6 (engine head) via an inner passage 51
through inner tube 50, while fuel from second common rail 16 is
moved to fuel injector 12 in an outer passage 49 defined between
inner tube 50 and an outer tube 40. Inner tube 50 may be of a
familiar construction to those skilled in the art, in that it
includes rounded or conical ends that are compressed between a
conical seat 38 of quill 30 and an inner conical seat 55 of fuel
injector 12. Thus, the fluid passage 51 within inner tube 50
extends between first fuel outlet 34 of quill 30 and an inner fuel
inlet 57 of fuel injector 12. Outer tube 40, which may have no
contact with inner tube 50, has an inner diameter larger than an
outer diameter of inner tube 50 in order to define an elongate
outer passage 49 that opens on one end to second fuel outlet 37 of
quill 30 and at its other end to an outer fuel inlet 48 of fuel
injector 12. Outer tube 40 includes a rounded or conical end that
is compressed into sealing contact with outer conical seat 46 of
fuel injector 12. The outer fuel inlet 48 opens between the inner
diameter of tube 40 and the outer surface of inner tube 50. Thus,
fuel injector 12 defines an outer conical seat 46 that
concentrically surrounds an inner conical seat 55. In addition, the
fuel injector 12 includes an inner fuel inlet 57 surrounded by the
inner conical seat 55, and an outer fuel inlet 48 positioned
between the inner conical seat 57 and the outer conical seat
46.
[0021] Outer tube 40 is compressed between quill 30 and the fuel
injector 12. In particular, outer tube 40 includes a rounded or
conical end in sealing contact with outer conical seat 46 and an
opposite end received in a bore defined by quill 30. One end 41 of
outer tube 40 is sealed via an O-ring 80 that is positioned in a
space 45 between outer tube 40 and quill 30. O-ring 80 is
maintained in place against the pressure from second common rail 16
by a back up ring 86 held in place by a cap 87 threaded to quill
30. Outer tube 40 is compressed onto outer seat 46 of fuel injector
12 by an axial force applied to a load shoulder 42 by a compression
load adjuster 60 that includes a contact surface 64 in contact with
load shoulder 42. Compression load adjuster 60 includes outer
threads 65 that mate with a set of inner threads defined by base
121 of block 120, and includes a tool engagement surface 62 located
in hollow interior 124 of block 120 to facilitate adjusting a
compression load on outer tube 40. Thus, leakage of the second fuel
from common rail 16 to atmosphere is inhibited by setting a
compression load on the outer tube 40 with compression load
adjuster 60 above a predetermined threshold to facilitate a seal at
outer conical seat 46, and by sealing the other end with o-ring
80.
[0022] Sealing at opposite ends of inner tube 50 is facilitated by
a separate load adjuster 66 that includes threads 68 mated to
internal threads defined by base 121 of block 120. Load adjuster 66
includes a tool engagement surface 67 located outside of block 20
that facilitates movement of compression load adjuster 66 along a
common centerline 54. In other words, compression load adjuster 66
pushes along common centerline 54 against quill 30 to compress
inner tube 50 between conical seat 38 of quill 30 and conical seat
55 of fuel injector 12. Because one end 41 of outer tube 40 can
slide within quill 30, the respective compression loads on inner
tube 50 and outer tube 40 can be adjusted independently to better
insure proper sealing at all of the conical seats 38, 55 and 46.
Thus, leakage of the first fuel originating from common rail 14
into the second fuel is inhibited by setting a compression load on
the inner tube 50 above a predetermined threshold with compression
load adjuster 66. In addition, leakage of the second fuel from
common rail 16 into the first fuel from common rail 14 may include
setting the pressure in common rail 14 higher than the pressure in
common rail 16. Outer tube 40, inner tube 50, compression load
adjuster 60, compression load adjuster 66, conical seat 38, inner
conical seat 55 and outer conical seat 46 all share a common
centerline 54. Other sealing strategies for one or both of inner
tube 50 and outer tube 40 apart from that described in relation to
the drawings also fall within the contemplated scope of the present
disclosure.
[0023] As shown, quill 30 may be at least partially positioned
within block 120, which includes a base 121 and a cover 122 that
may be attached to base 121 by a plurality of fasteners 126. Base
121 may include a flange that facilitates attachment of block 120
to an engine head (housing 6) via bolts (not shown). As shown in
the Figures, the first fuel inlet 33 and the second fuel inlet 36
of quill 30 may be located outside of block 120. A shim 127 may be
included to adjust the distance between conical seat 38 and conical
seat 57 to compensate for geometrical tolerances in the fuel system
and engine components. Any of the second fuel that manages to leak
past O-ring 80 into hollow interior 124 of block 120, may be vented
to atmosphere via vent opening 123. Thus, vent opening 123 might be
eliminated in a case where the fuel in common rail 16 is not
gaseous at atmospheric pressure. Except for vent opening 123,
hollow interior 24 may be substantially closed via an O-ring 81
that is in contact with quill 30 and block 120 and surrounds first
fuel passage 32. In addition, a second O-ring 82 may be in contact
with quill 30 and block 120 and surround the second fuel passage
35. Thus, vent opening 123 extends between hollow interior 125 and
an outer surface 125 of block 120, which is exposed to
atmosphere.
[0024] Coaxial quill assembly 118 may also include a flange 83,
collar 85 and bolts 84 to facilitate a sealed fluid connection
between quill 30 and common rail 14. Although co-axial quill
assembly 118 is illustrated as including a separate block 120 and
quill 30, those skilled in the art will appreciate that the
functions and structures of those two components could be merged
into a single component without departing from the present
disclosure.
[0025] Referring now to FIGS. 3-5, each of the fuel injectors 12
includes two control valves 76 that are individually actuated via a
dual solenoid actuator 100 in control communication with electronic
controller 15. In the illustrated embodiment, the two control
valves 76 are each two way valves that open and close respective
pressure relief passageways 111 and 112 to a low pressure drain
outlet 77. As shown in FIG. 1, drain outlet 77 is fluidly connected
to tank 23 via a drain return line 24. Thus, those skilled in the
art will recognize that all of the control functions for fuel
injector 12 are performed using the liquid fuel as a hydraulic
medium in a manner well known in the art. FIGS. 4 and 5 show two
different versions of a bottom portion of fuel injector 12. FIG. 4
shows a version in which the fuel injector has concentric sets of
gas nozzle outlets 90a and a liquid set of fuel nozzle outlets 96a,
whereas FIG. 5 shows a configuration in which the gas nozzle
outlets 90b are side by side with the liquid fuel nozzle outlets
96b. In the embodiment of FIG. 5, liquid needle valve member 78b
moves along a centerline 79b, and gas needle valve member 73b moves
along a centerline 89b that is parallel to, but offset from,
centerline 79b. Identical features in the two different fuel
injector versions are identified with the same numerals, but the
numerals include an "a" in the case of the dual concentric
configuration of FIG. 4, and include a designation "b" in the case
of the side by side version of FIG. 5. In both versions, the
respective gas needle valve member 73 and liquid needle valve
member 78 seat at different locations on the same tip component 71
of the injector body 70.
[0026] As shown in FIG. 3, a dual solenoid actuator 100 may be
utilized for controlling the two control valves 76 in different
configurations to provide a noninjection configuration, a liquid or
diesel fuel injection configuration, a gaseous fuel injection
configuration, and even a combined injection configuration. Dual
solenoid 100 is shown in its noninjection configuration with a
first armature 110 in an unenergized position and a second armature
103 in an unenergized position. First armature 110 is connected to
a pusher 106 by an armature attachment 107 to hold valve member 154
in a upward closed position in contact with flat seat 151 under the
action of shared spring 115. When valve member 154 is in its upward
closed position, pressure in pressure control chamber 92 (and
pressure relief passage 111) is high (rail pressure) and acts upon
closing hydraulic surface 61 of gas needle valve member 73 to
maintain it in its downward closed position to close gas nozzle
outlets 90.
[0027] Second armature 103 is connected to a pusher 108 by a second
armature attachment 109 to urge valve member 153 into contact with
flat valve seat 150 by shared spring 115. When valve member 153 is
in its downward closed position, pressure in second pressure
control chamber 95 (and pressure relief passage 112) is high (rail
pressure) and acts on closing hydraulic surface 58 to help urge
diesel needle valve member 78 downward to close liquid nozzle
outlets 96. When armatures 110 and 103 are in their unenergized
positions, coils 102 and 104 may be in respective unenergized
states. It should be noted that dual solenoid actuator 100 utilizes
a common or shared stator 105 upon which both coils 102 and 104 are
mounted. Thus, magnetic flux necessary to move armature 110 or
armature 103, or both is carried by shared stator 105. Valve
members 153 and 154 may be made from ceramics and may be
un-attached to their respective pushers 108 and 106.
[0028] In order to initiate a gas injection event, dual solenoid
actuator 100 is changed to a first fuel injection configuration by
energizing coil 104 to pull armature 110 downward toward an
energized position until the movement of pusher 106 (and armature
110) is arrested by a stop (not shown). When this occurs, valve
member 154 moves (is pushed off of seat by high pressure) to an
open position out of contact with the flat seat 151 to fluidly
connect pressure control chamber 92 and pressure relief passage 111
to low pressure drain 77 via hidden passages shown schematically by
dotted lines. When this occurs, the pressure acting on closing
hydraulic surface 61 decreases and is overcome by the pressure
acting on opening hydraulic surface 69, causing gas needle valve
member 89 to move upward to open gas nozzle outlets 90 to the gas
fuel inlet 48 (FIG. 2). When it becomes time to end the gaseous
fuel injection event, coil 104 is de-energized. This allows shared
spring 115 to push valve member 154 back upward into contact with
flat seat 151 to block pressure relief passage 111 to increase
pressure on closing hydraulic surface 61, causing gas needle valve
member 73 to move downward to close the gas set of nozzle outlets
90.
[0029] A liquid fuel injection event may be initiated by energizing
coil 102 to move armature 103 from its unenergized position to its
energized position closer to coil 102. When this occurs, pusher 108
is moved upward to permit valve member 153 to move to an open
position out of contact with flat seat 150 due to pressure in
relief passage 112. When this occurs, pressure control chamber 95
and pressure relief passage 112 become fluidly connected to low
pressure drain 77 (via hidden passages shown schematically by
dotted lined) causing the pressure on closing hydraulic surface 58
to drop. When this occurs, the pressure acting on opening hydraulic
surface 59 causes diesel needle valve member 78 to move upward to
open the liquid set of nozzle outlets 96 to the liquid fuel inlet
57 (FIG. 2). When it comes time to end a liquid fuel injection
event, coil 102 may be de-energized. Shared spring 115 then acts on
pusher 108 to move armature 103 back upward toward the unenergized
position and move valve member 153 back to its closed position in
contact with flat valve seat 150 to close the fluid connection
between pressure control chamber 95 and low pressure drain 77. When
this occurs, pressure on closing hydraulic surface 58 again rises
causing diesel needle valve member 78 to move downward to close the
liquid set of nozzle outlets 96.
[0030] Because dual solenoid actuator 100 can cause valve member
154 and 153 to move to their open positions independently, the dual
solenoid actuator 100 also can facilitate a combined injection
configuration in which both coils 102 and 104 are energized
simultaneously. Armature 110, coil 102, armature 103, coil 104
pusher 106, valve member 154, pusher 108 and valve member 153 may
share a common centerline 88. It should be noted that whenever an
injection occurs, one of the armatures 110 and 103 moves toward the
other of the armature 110 and 103 along common centerline 88.
[0031] Referring now to FIG. 6, during a gas injection event, one
of the two control valves 76 is actuated to fluidly connect a
pressure control chamber 92 to drain outlet 77. In other words,
valve member 154 moves into and out of contact with valve seat 151
responsive to movement of armature 110 between an unenergized
position and an energized position, respectively. When this is
done, pressure in control chamber 92 drops allowing a gas needle 73
to lift toward an open position against the action of a biasing
spring to fluidly connect a gas nozzle chamber 91 to gas nozzle
outlets 90. When fuel injector 12 is in a gas injection
configuration, the liquid fuel common rail 14 is fluidly connected
to drain outlet 77 since pressure control chamber 92 is always
fluidly connected to a liquid nozzle supply passage 98 through a
small orifice. Liquid nozzle supply passage 98 is always fluidly
connected to inner fuel inlet 57 (FIG. 2). When the two control
valves 76 are in a liquid injection configuration, the other of the
two valves is actuated to fluidly connect the liquid common rail 14
to the drain outlet 77 through a second pressure control chamber
95, which is also always fluidly connected to high pressure in
liquid nozzle supply passage 98. In other words, control valve
member 153 moves into and out of contact with valve seat 150
responsive to movement of armature 103 between an unenergized
position and an energized position, respectively. The two control
valves 76 also have a combined injection configuration at which
both of the two control valves 76 are moved to an open position so
that the liquid fuel common rail 14 is fluidly connected to the
drain outlet 77 through the first pressure control chamber 92 and
in parallel through the second control pressure chamber 95.
Finally, the two control valves 76 have a non-injection
configuration at which the liquid fuel common rail 14 is blocked
from the drain outlet 77 by having both of the two control valves
76 in a closed position.
[0032] In both versions of fuel injector 12 in FIGS. 4 and 5, a gas
needle valve member 73 is positioned completely inside of injector
body 70 with a guide surface 75 extending in a guide component 72
of injector body 70 between the first pressure control chamber 92
and the gas nozzle chamber 91. The gas nozzle chamber 91 is always
fluidly connected to the gaseous fuel common rail 16, and is
therefore at about the same pressure as the gaseous fuel common
rail 16. A segment 74 of gas needle 73 and the guide component 72
define a portion of an annular volume 94 that is always fluidly
connected to liquid common rail 14 via a branch passage that is
fluidly connected to liquid nozzle supply passage 98. This
structure may help to maintain lubricity and hydraulic locking in
the guide clearance 93.
INDUSTRIAL APPLICABILITY
[0033] The dual fuel common rail system 10 of the present
disclosure finds general applicability to any engine that utilizes
two fuels in the combustion space of an associated engine. These
two fuels may be the same fuel at two different pressures, or may,
as in the illustrated embodiment be different fuels. Although the
present disclosure could apply to spark ignited engines utilizing
appropriate fuels, the present disclosure finds particular
applicability in gaseous fuel engines that utilize a relatively
large charge of natural gas that is ignited via compression
ignition of a small charge of distillate diesel fuel originating
from common rail 14. The coaxial quill assembly 118 of the present
disclosure can facilitate movement of both fuels to a fuel injector
12 mounted in the head 6 of an engine 5 via a single bore through
the engine head associated with each fuel injector 12 of the engine
5. This strategy conserves valuable space in and around the
engine.
[0034] By utilizing a block 120 that is bolted to the outer surface
of the engine head, separate load adjusters 60 and 66 can be
utilized to independently load the inner tube 50 and outer tube 40
onto the conical seats 57 and 46, respectively of fuel injector 12
to inhibit fuel leakage between the fuels and to inhibit fuel
leakage to atmosphere outside of fuel injector 12, while accounting
for slight dimensional differences associated with each fuel
injector fluid connection.
[0035] When in operation, the first fuel (distillate diesel) at a
first pressure moves from first common rail 14 through the first
fuel passage 32, through inner tube 50 and into fuel injector 12.
The second fuel (natural gas) at a second pressure is moved from
the second common rail 16 through the second fuel passage 35,
through the outer passage 49 between outer tube 40 and inner tube
50 and into fuel injector 12. Leakage of the second fuel to the
first fuel may be inhibited by setting the pressure in common rail
14 to a medium high pressure (maybe about 40 MPa) that is higher
than the pressure in common rail 16, which may be maintained to a
medium low pressure (maybe about 35 MPa). Inhibiting leakage of the
liquid fuel into the gaseous fuel includes setting a compression
load on the inner tube 50 above a first predetermined threshold
with the compression load adjuster 66 to create appropriate sealing
forces on both ends of tube 50. Leakage of the second fuel to
atmosphere may be inhibited by setting a compression load on the
outer tube 40 above a second predetermined threshold with the
second load adjuster 60 to create a seal between outer tube 40 and
fuel injector 12. Leakage of gaseous fuel to atmosphere is
inhibited by including at least one o-ring, such as o-ring 80 in
contact with outer tube 40. Nevertheless, those skilled in the art
will appreciate that other concentric tube supply arrangements
could be utilized without departing from the present disclosure.
However, in the illustrated embodiment, leakage and variations in
geometrical tolerances in the various components of engine 5 and
fuel system 10 can be accommodated by utilizing first and second
compression load adjusters 60 and 66 to respectively adjust the
compression loads in the outer tube 40 and the inner tube 50
individually.
[0036] The fuel system 10 according to the present disclosure also
includes several subtle functions providing advantages over known
dual fuel systems. Among these are independent injection control
via separate valves and separate electrical actuators for each of
the gas and liquid systems. Thus, the fuel injector 12 can be
controlled to inject gaseous fuel only, liquid fuel only, both
gaseous and liquid fuel simultaneously, and of course have
non-injection mode when no injection occurs. In addition, the dual
solenoid actuator 100 conserves space without sacrificing
performance capabilities. Although the migration of gaseous fuel
into the liquid fuel is generally inhibited by maintaining the
liquid fuel common rail 14 at a higher pressure than the gaseous
fuel common rail 16, other subtle but important features assist in
preventing such leakage. Cross leakage issues are also inhibited by
locating the liquid fuel supply in the inner tube 50, and locating
the gaseous fuel supply to injectors 12 in the outer passage 49
between inner tube 50 and outer tube 40. By locating these
passageways concentrically, each fuel injector 12 can be supplied
with both fuels via one passageway through the engine housing 6
(head) rather than two passageways. Lubricity of the moving
components within the fuel injector 12 may be maintained by
exposure to liquid diesel fuel. For instance, the guide clearance
93 associated with gas needle 73 is maintained with liquid diesel
fuel to maintain lubricity, even though one end of the gas needle
73 is always exposed to gaseous fuel in gas nozzle chamber 91.
[0037] By utilizing the concentric supply strategy, the fuel system
10 of the present disclosure presents a potential opportunity for
retrofitting existing engines with minimized engine cylinder head
modifications. The structure of the several versions of fuel
injectors 12 also inhibits the leakage of gaseous fuel into the
engine cylinder by locating both the gaseous fuel nozzle outlets 90
and the liquid fuel nozzle outlets 96 in a single tip component 71,
rather than via some nested needle strategy of a type known in the
art. Thus, the fuel injector 12 of the present disclosure avoids
stacked tolerances and other uncertainties by making each of the
gas and liquid needle structures independent in their movement,
seating and biasing features. This strategy may better enable mass
production of fuel injectors that perform consistently with the
same control signals. Finally the engine 5 of the present
disclosure contemplates both a normal dual fueling mode and a limp
home mode in which only liquid fuel is injected. For instance, if a
malfunction occurs in the gaseous fuel system or if the gaseous
fuel supply is exhausted, the electronic controller 15 may cause or
allow the engine to switch from a dual fueling mode to the limp
home mode.
[0038] As best shown in FIG. 6, the dual fueling mode is
characterized by a large gas injection quantity 138 and a small
quantity injection 135 of liquid fuel. On the otherhand, the limp
home mode may be characterized by no gas injection but a large
quantity 136 liquid fuel injection. In addition, the normal dual
fueling mode is characterized by the gas and liquid common rails 16
and 14 being maintained at medium low and medium high pressures,
respectively. On the otherhand, the limp home mode may be
characterized by the gaseous fuel common rail being allowed to
decay to, or be maintained at, a low pressure, while pressure in
the liquid common rail 14 is increased to a high pressure 133
(maybe greater than 100 MPa). When operating in the dual fueling
mode, a relatively small injection of liquid distillate diesel fuel
is compression ignited to in turn ignite a relatively large charge
of gaseous fuel, which may at least partially have been previously
injected into the engine cylinder. On the otherhand, during a limp
home mode, engine 5 functions as a somewhat conventional diesel
engine in which a relatively large quantity of liquid fuel is
injected at or around top dead center of the compression stroke to
instantaneously ignite upon injection in a known manner.
[0039] The present description is for illustrative purposes only,
and should not be construed to narrow the breadth of the present
disclosure in any way. Thus, those skilled in the art will
appreciate that various modifications might be made to the
presently disclosed embodiments without departing from the full and
fair scope and spirit of the present disclosure. Other aspects,
features and advantages will be apparent upon an examination of the
attached drawings and appended claims.
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